A typical magnetic disk drive includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic transitions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
FIG. 1 is a side cross-sectional elevation view of a piggyback magnetic head 100, which includes a write head portion 102 and a read head portion 104, the read head portion employing a spin valve sensor 106. FIG. 2 is an air bearing surface (ABS) view of FIG. 1. The spin valve sensor 106 is sandwiched between nonmagnetic electrically insulative first and second read gap layers 108 and 110, and the read gap layers are sandwiched between ferromagnetic first and second shield layers 112 and 114. In response to external magnetic fields, the resistance of the spin valve sensor 106 changes. A sense current (Is) conducted through the sensor causes these resistance changes to be manifested as potential changes. These potential changes are then processed as readback signals by processing circuitry.
The write head portion 102 of the magnetic head 100 includes a first coil layer 122 embedded in a first insulation layer 116. A second insulation layer 120 is employed to planarize the head after the second pole tip process so that a subsequent second layer coil can be formed on a substantially planar surface. A second coil layer 123 is embedded in a third insulation layer 125. The first, second, and third insulation layers are referred to in the art as an “insulation stack”. The coil layers 122, 123 and the first, second and third insulation layers 116, 120 and 125 are sandwiched between first and second pole piece layers 124 and 126. The first and second pole piece layers 124 and 126 are magnetically coupled at a back gap 128 and have first and second pole tips 131 and 132 which are separated by a write gap layer 134 at the ABS. In a merged head, the second shield layer 114 and the first pole piece layer 124 would be a common layer.
In a conventional design, a bump 136 is formed on the write gap layer 134 to form a stitched structure. However, there are certain limitations on creating the bump 136. One problem encountered when attempting to form this bump 136 is that small variations of the bump 136 have a dramatic effect on the write function. Particularly, if the bump 136 is too tall in a direction parallel to the ABS, the amount of magnetic material on the top of the bump will be reduced. The large topography of a large bump height also makes if difficult to form the track width of the second pole tip 132 due to the reflective light during the photolithography process. If the bump 136 is too short, leakage across the write gap occurs, which in turn reduces write efficiency.
What is needed is a structure that has a height sufficient to separate the first and second pole tips 131 and 132, but at the same time not creating too much topography when the second pole tip 132 and second pole piece layer 126 are formed.
What is also needed is a bump structure that provides controlled P1 saturation.
What is further needed is a structure that has a reduced throat height to improve write efficiency for lower track width/write gap length used in future high density heads.
What is still further needed is a bump formed using a dry process for good throat height definition.